74
platforms include free-floating buoys (surface or profiling), autonomous surface
craft, autonomous underwater vehicles, buoyancy-driven gliders, and the innovative
wave gliders and saildrones. Unmanned satellites now constitute an essential
resource for remote sensing of ocean surface and near-surface properties. All such
platforms can incorporate a variety of instruments and sensors including still and
video cameras.
3.2.1 Manned Vessels and Shipboard Deployed Vehicles
Instruments deployed on lowered cables have been a fixture of oceanographic
research since the HMS CHALLENGER expedition (1872–1976) when thermometers and sampling bottles were routinely deployed to full ocean depth using hemp
rope and lead weights, including, remarkably, the sounding in the Marianas Trench
of the aptly named Challenger Deep, the deepest part of the world ocean at greater
than 11 km. Today, the carrousel or rosette sampler (a cylindrical frame fitted with
oceanographic sampling bottles, sensors, and data links) is a common sight aboard
oceanographic and survey vessels.
Hydraulic or electric spooling winches equipped with single- or multipleconductor electromechanical cable deploy these carrousel-like platforms. Slip-ring
devices mounted on the winch axle allow instrument data and ship-board commands
and power for bottle operation to flow through the cable’s electrical conductors to
and from the operation consoles so that instrumental data output may be viewed in
real time and bottles may be remotely triggered from the surface vessel at standard
or selected depths (Fig. 3.6).
These instruments are usually deployed from a stationary vessel which contributes to the expense of their operation since ship time can be valued in the tens of
thousands of dollars per day and a shallow deployment can consume 1 h or more of
ship time. To address this issue, fast CTDs coupled to specialized underway winches
now allow profiles to depths of 400 m while underway at 10 knots but cannot
retrieve subsurface water samples.
A different approach to these recoverable instruments is embodied in expendable
instruments such as the expendable bathythermograph (XBT), a probe developed
originally for defense applications. This instrument consists of an expendable
ballasted probe carrying a thermistor sensor connected through a launcher to a
shipboard console. Upon descent, the streamlined probes and the handheld or deckmounted launcher both unwind thin conductive copper wires from internal spools.
The probes rapidly achieve terminal velocity allowing calculation of depth from the
time the probe strikes the water dispensing with the need for a separate pressure
(depth) sensor. Expendable CTDs, based upon this model, but with an additional
conductivity sensor, have been available for some time. Such probes can be deployed
from a moving vessel.
Modern research and survey vessels also mount flow-through instruments that
allow continuous sampling of near surface waters while underway. Water is taken in
3 Platforms for Coastal Ocean Observing
platforms include free-floating buoys (surface or profiling), autonomous surface
craft, autonomous underwater vehicles, buoyancy-driven gliders, and the innovative
wave gliders and saildrones. Unmanned satellites now constitute an essential
resource for remote sensing of ocean surface and near-surface properties. All such
platforms can incorporate a variety of instruments and sensors including still and
video cameras.
3.2.1 Manned Vessels and Shipboard Deployed Vehicles
Instruments deployed on lowered cables have been a fixture of oceanographic
research since the HMS CHALLENGER expedition (1872–1976) when thermometers and sampling bottles were routinely deployed to full ocean depth using hemp
rope and lead weights, including, remarkably, the sounding in the Marianas Trench
of the aptly named Challenger Deep, the deepest part of the world ocean at greater
than 11 km. Today, the carrousel or rosette sampler (a cylindrical frame fitted with
oceanographic sampling bottles, sensors, and data links) is a common sight aboard
oceanographic and survey vessels.
Hydraulic or electric spooling winches equipped with single- or multipleconductor electromechanical cable deploy these carrousel-like platforms. Slip-ring
devices mounted on the winch axle allow instrument data and ship-board commands
and power for bottle operation to flow through the cable’s electrical conductors to
and from the operation consoles so that instrumental data output may be viewed in
real time and bottles may be remotely triggered from the surface vessel at standard
or selected depths (Fig. 3.6).
These instruments are usually deployed from a stationary vessel which contributes to the expense of their operation since ship time can be valued in the tens of
thousands of dollars per day and a shallow deployment can consume 1 h or more of
ship time. To address this issue, fast CTDs coupled to specialized underway winches
now allow profiles to depths of 400 m while underway at 10 knots but cannot
retrieve subsurface water samples.
A different approach to these recoverable instruments is embodied in expendable
instruments such as the expendable bathythermograph (XBT), a probe developed
originally for defense applications. This instrument consists of an expendable
ballasted probe carrying a thermistor sensor connected through a launcher to a
shipboard console. Upon descent, the streamlined probes and the handheld or deckmounted launcher both unwind thin conductive copper wires from internal spools.
The probes rapidly achieve terminal velocity allowing calculation of depth from the
time the probe strikes the water dispensing with the need for a separate pressure
(depth) sensor. Expendable CTDs, based upon this model, but with an additional
conductivity sensor, have been available for some time. Such probes can be deployed
from a moving vessel.
Modern research and survey vessels also mount flow-through instruments that
allow continuous sampling of near surface waters while underway. Water is taken in
3 Platforms for Coastal Ocean Observing